Thermostat



y 22, 1941. R112. LEE 2,249,837

' THERMOSTAT Filed Au 27, I938 i La 5 94 P 46 as 22 P8 19 7 1 :94. Fig 5.

INVENTOR Paul B. Lee.

ATTOR'NEY Patented July 22, 1941 UNITED STATES PATENT OFFICE THERMOSTAT Paul R. Lee, Mansfield, Ohio, assignor to Westinghouse Electric & Manufacturing Company, mltastlittsburgh, Pa., a corporation of Pennsyl- Applicaflon August 27, 1938, Serial N0. 227,076

8 Claims. (CL 200-138) My invention relates to thermostats, and more particularly to the mounting of a bimetallic member therefor.

An object of my invention is to provide a thermostat having a three-legged snap-acting bimetallic member anchored to a supporting structure by means of the center leg, whereby the operation of the bimetallic member is regulated through the adjustable movements of a cooperating stationary contact by varying the relative positions of thestationary contact with respect to the member, so as to vary the curvature of the intermediate leg.

Another object of my invention is to provide a method of mounting a bimetallic member in a thermostat which will permit the opening temperature of such member to be readily manually adjusted without afiecting the closing temperature of such member.

A further object of my invention is to elimihollow portion 28, a transversely positioned unnate any restraining action upon the bimetallic pointed out specifically in the course of the following description of a device embodying my invention, or will be apparent from such description.

In the accompanying drawing:

Figures 1 and 2 are, respectively, top and side elevational views of the devices embodying my invention;

Fig. 3 is asectional view taken along the line III-Ill. of Fig. 1;

Figs. 4 and 5 are plan and perspective views of a bimetallic member for the devices embodying my invention;

Fig. 6 is a perspective view of a modified form of the member shown in Figs. 4 and 5; and

Fig. 7 is a side elevational view of the member shown in Fig. 5, partially mounted.

Referring to the accompanying drawing, I show a thermostat [0 comprising a supporting structure or base l2, a bimetallic snap-acting thermal responsive member I4, a supporting rivet l6 for rigidly attaching the member H to the supporting structure I2, contact means including a movable contact I 8 and a stationary contact 20, a terminal bracket 2|, and suitable adjusting means 22 operatively associated with the supporting der-cut or slot portion 24, for receiving the terminal bracket 2i, an aperture 25, extending through the base from the under-cut portion 2| to the inner hollow portion 26 for retaining the supporting rivet i5, and an internally threaded brass insert 28 extending therethrough, for receiving the adjusting screw 22, as hereinafter described.

The bimetallic member I4 is formed preferably from a single or unitary standard sheet of bimetallic material and preferably has the high expansion side thereof positioned on the upper side. Two slots 30, in this instance substantially arcuate in shape, are located longitudinally within the member i4 and define a central strip and two exterior lateral strips 42. However, it is to be understood that the slots may be formed in the bimetallic sheet in any desired shape, and that, if desired, the bimetallic member may be otherwise fabricated from a plurality of elements. In addition to the arcuate slots 30, a small circular aperture 32 is positioned substantially in line with two corresponding ends of the slots 30, and more particularly, substantially mid-way between such ends. It, therefore, follows that, in this instance, a portion of the aperture 32 extends into the central strip 40 for a purpose hereinafter described. The bimetallic member ll, after having the slots 30 and aperture 32 positioned therethrough, is bowed and heat-treated in such a manner that the central strip 40 is bowed outwardly and downwardly a greater amount than the exterior strips, with the high expansive side of the bimetallic member positioned on the upper surface. In other words, the central strip is bowed outwardly with respect to the other strips. The central strip will then be concave upwardly or convex downwardly. The .bimetallic member is thus formed in such a manner so as to insure a snap-acting action of such member as it flexes from one operative position to another.

The rivet It comprises, in this instance, a centrally disposed enlarged portion 34, an upwardly extending shank 36 and a downwardly extending shank 38. The upwardly extending shank 36 is adapted to extend through the aperture 25 of base l2, while the lower extending shank 38 is adapted to extend through the aperture 32 of the bimetallic member I4, so as to rigidly attach the member to the base i2. The rivet l6 may be of any material desired. However, it is preferred that it be of such metal which will freely permit the ends of the shanks 35 and 33 to be spun over as hereinafter described.

The movable contact 3 is rigidly attached to the free end of the member l4, and, in this instance, is positioned upon the upper surface thereof. The contact I8 is electrically associated with the member l4 to permit the passage of current therethrough. However, it is to be understood that, if desired, the movable contact means l8 may be insulatedly attached to the member l4.

The stationary contact 20 is rigidly attached to or integral with the lower end of the adjusting screw 22 and is adapted to cooperate with the movable contact l8. The adjusting screw 22 is threadedly attached to the base l2 through the cooperation of an internally threaded insert 28 which is rigidly attached to the base [2. The adjusting screw 22, upon being rotated within the insert 28, bodily moves the stationary contact 20 with respect to the base l2 and bimetallic member l4 so as to vary the opening temperature of such member l4, as hereinafter described.

When assembling the thermostat l after the bimetallic member l4 has been pre-shaped and heat-treated substantially as hereinabove described, the lower shank portion 38 of rivet I 6 is positioned through the aperture 32 of bimetallic member l4, whereupon the main body portion 34 of the rivet will rest upon the upper surface of the bimetallic member. Inasmuch as the main body portion 34 is substantially larger than the aperture 32, it is obvious that such portion will extend a substantial distance into the central leg 40 for a purpose hereinafter described. A washer 44 is then positioned upon the shank portion 38 against the lower surface of the bimetallic member'M, whereupon the lower end of the shank 38 is spun or riveted over tightly against the washer 44 to rigidly attach the bimetallic member to the rivet Hi. The bimetallic member l4 and rivet 16 are then positioned within the inner hollow portion 26 of base l2 and the upper shank portion 36 of rivet I6 is inserted through the aperture 25 in the base 12. The angular terminal bracket 2| is then positioned about the shank portion 36 and within the undercut portion 24 of base l2, whereupon the upper end of the shank 36 is welded or spun over tightly against the bracket substantially as shown at 46 in Fig. 3.

It is, therefore, obvious that, inasmuch as the rivet l8 extends a substantial distance into the central strip or leg 40, such rivet rigidly attaches the bimetallic member I4 to the supporting structure l2 by direct cooperation with the central strip as distinguished from the exterior strips 42. It is obvious that the exact position of the aperture 32 is not dominating providing the rivet 16 extends a substantial distance into the central strip 40, so that the rivet will rigidly attach the bimetallic member to the supporting structure by direct cooperation with the central strip 40.

When operating the thermostat in conjunction with an electrical circuit (not shown), the operation of which it is desired to control, one lead of the circuit is connected to the angular terminal bracket 2| and the second lead is connected to adjusting screw 22. The second lead is inserted within a counter-bore 23 positioned within the upper end of the screw 22 and, say, soldered thereto. The circuit through the thermostat is then substantially as follows: from the bracket 2|, through bimetallic member [4, movable contact l8, and stationary contact 20 to adjusting screw 22. Inasmuch as the bimetallic member I4 is positioned within the circuit, it follows that the temperature of such member will increase in proportion to the current passing therethrough.

As the temperature of the bimetallic member 14 increases, the central leg tends to change its curvature and, as the temperature of the member 14 reaches its predetermined opening temperature, finally does so change its curvature. As the central leg changes its curvature from concave upwardly to convex downwardly, the free end of member M will be moved downwardly with a snap action, causing the circuit therethrough to be broken. The temperature of the member l4 will then decrease and, upon reaching the predetermined closing value, the bimetallic member will flex to a closed position, whereupon the contacts l8 and 20 will be reengaged and current will again be permitted to pass through the thermostat Ill and the controlled circuit.

Inasmuch as the rivet I6 is rigidly attached to the central strip 40 of the bimetallic member l4, it follows that as the adjusting screw 22 is run down within the insert 28, the additional pressure therefrom is directed on substantially the end of the bimetallic member I 4 through the cooperation of contacts l8 and 20, loading the central strip 40 of the bimetallic member in a manner similar to a cantilever type beam having a concentrated load at one end. In other words, the bimetallic member [4 and the central strip 40 will be bent downwardly in response to the downward movement of the adjusting screw 22. The downward pressure supplied by the adlusting screw 22 tends to reverse the curvature in the central strip 40, which thus tends to buckle into a position opposite to the normal position, or convex upwardly.

As the downward pressure supplied by the adjusting screw 22 increases and the curvature of the central strip changes, the opening temperature of the bimetallic member will decrease, it being understood that the opening temperature is inherently decreased primarily by a change in curvature of the central strip. It follows that, to increase the opening temperature of the thermostat. adjusting screw 22 may be run out within the insert 28 so as to reduce the pressure on the free end of bimetallic member l4 and to reduce the tendency for the central strip to change its curvature. It is obvious that the exterior legs 42 will to a small degree change their curvature with a change in curvature of the central strip Inasmuch as the adjusting screw 22 is operatively associated with the bimetallic member l4, only when the thermostat is in a closed position, the adjusting screw cannot substantially effect the closing temperature of the thermostat. It, therefore, follows that the adjusting means, namely, adjusting screw 22, operatively associated with the bimetallic member I4 and supporting structure [2, changes the curvature of the central strip 40 while the thermostat is in a closed position only, for adjusting the opening temperature of the thermostat without substantially effecting a change in the closing temperature of such thermostat. However, it is obvious that by placing a corresponding adjusting means, either singularly or in combination with the adjusting screw 22, on the lower side of the bimetallic member H, the closing temperature thereoi' could likewise be adjusted, either independently or in combination with the adjustment of the opening temperature.

The aperture 32. and rivet i6 are positioned upon the bimetallic member ll so as to extend into the central strip l0, inasmuch as it is desired to have the pressure applied by the adjusting screw 22 cause the curvature of the central strip 40 to change. Should the aperture 22 and rivet l8 be positioned closer to the end of the bimetallic member II, in such a manner that the rivet l6 would not extend into the central strip 40, the pressure applied by the adjusting screw 22 will tend to bias the bimetallic member l4 downwardly as a cantilever beam from the rivet i6 as a fulcrum, without substantially afi'ecting the independent curvature of the central strip 40. Accordingly, inasmuch as the curvature of the central strip 40 must be changed considerably more thanthat of the exterior strips 42 to vary the opening temperature of the thermostat, it follows that the aperture 32 and especially the rivet l6, must extend into the central strip 40 to permit the pressure supplied by the adjusting screw 22 to change the curvature of the central strip and to adjust the opening temperature of the thermostat.

Inasmuch as the bimetallic member l4 when in an open position is separated from the adjusting screw 22, it is apparent that the reclosing temperature of such bimetallic member cannot be effected by the relative movements of the adjusting screw 22. It is, therefore, obvious that the adjusting screw 22 including the stationary contact 20, due to the manual adjustment thereof, adjusts the opening temperature of the thermostat without substantially effecting a change in the closing temperature thereof.

Various modifications may be made in the device embodying my invention without departing from the spirit and scope thereof, such as utilizing only two legs with a central slot, and I desire, therefore, that only such limitations shall be placed thereon as are imposed by the prior art and the appended claims.

I claim as my invention:

l. A thermostat comprising, in combination, a supporting structure, a bimetallic member having two slots therein defining a central strip, two exterior lateral strips and two end portions, there being an aperture partially within said central strip and partially within the adjacent end portion, and means inserted through said aperture and having a larger diameter than the aperture for directly cooperating with the central strip as distinguished from said exterior strips for rigidly attaching the member to the supporting structure.

2. A thermostat comprising, in combination, a supporting structure, a bimetallic member having two slots therein defining a central strip, two exterior lateral strips and two end portions, there being an aperture partially within said central strip and partially within the adjacent end portion, means inserted through said aperture and thereby directly cooperating with the central strip as distinguished from said exterior strips for rigidly attaching the member to the supporting structure, and means operatively associated with the member for adjusting the opening temperature of such member.

3. A thermostat comprising, in combination, a supporting structure, a bimetallic member having two slots therein defining a central strip and two exterior lateral strips, means directly cooperating with the central strip as distinguished from said exterior strips for rigidly attaching the member to the supporting structure, and means operatively associated with the member for changing the curvature of the central strip while the thermostat is in a closed position only for adjusting the opening temperature of the thermostat without substantially efi'ecting a-change in the closing temperature thereof.

4. A thermostat comprising, in combination, a supporting structure, a bimetallic member having two slots therein defining a central strip and two exterior lateral strips, a supporting rivet for rigidly attaching the member to the structure by direct cooperation with the central strip as distinguished from said exterior strips, contact means including at least one movable contact attached to the free end of the member and one stationary cooperating contact, an adjusting screw associated with the stationary contact, and means including the movements of the screw for changing the curvature of the central stripto adjust the opening temperature of the thermostat without substantially efl'ecting a change in the closing temperature thereof.

5. A thermostat comprising, in combination, a

, supporting structure, a bimetallic member having two slots therein defining a central strip and two exterior lateral strips, a supporting rivet extend-.

ing through an aperture in the member located substantially in line' with corresponding ends of the slots for rigidly attaching the member to the structure by direct cooperation with the central strip, and means operatively associated with the member for changing the curvature of the central strip to adjust the opening temperature of the thermostat without substantially efiecting a change in the closing temperature thereof.

6. A thermostat comprising, in combination, a supporting structure, a snap-acting bimetallic member having two slots therein defining a central and two exterior lateral slots, and an aperture located substantially in line with corresponding ends of the slots, a supporting rivet extending through the aperture and cooperating with the structure for rigidly attaching the member to the structure by direct cooperation with the central strip as distinguished from the exterior strips, contact means including a movable contact attached to the free end of the member and a stationary cooperating contact, an adjusting screw carrying the stationary contact, and means including said screw and movable contact for changing the curvature of the central strip while the thermostat is in a closed position only for adjusting the opening temperature of the thermostat without substantially eilfectlng a change in the closing temperature thereof.

7. A thermostat'comprising, in combination, a supporting structure, a bimetallic member having a plurality of strips at least one of which is bowed outwardly with respect to another strip, there being an aperture in only said bowed strip, and means directly cooperating with said aperture in the bowed strip as distinguished from said other strip for rigidly attaching the member to the supporting structure thereby to restrain movement of said bowed strip relative to said strips atleast one or which is bowed outwardly tinguished from said other strip iorrigidly attaching the member to the supporting structure thereby to cause a modified movement oi the bowed strip with respect to said other strip when 5 said adjusting means is operated.

PAUL R. LEE. 

